1. Field of the Invention
This invention relates to lens adjustment for an image input apparatus.
2. Description of the Prior Art
Heretofore, the mounting of a lens to an image input apparatus has been performed by a method such as that shown in FIG. 1. In FIG. 1, there is shown a mount 1 for mounting a lens 2, for which a C-mount is generally used in an image input apparatus because of its general applicability as illustrated in the present example. Within a body 3 of an image input apparatus are incorporated a COD as an imaging device and other circuits.
There are also shown an adjusting member 4 used when the mount 1 is mounted to the body 3, and a screw 5 for mounting the mount 1 to the body 3. An imaging device CCD 6, being a considerable heat source, is fixed to a radiating mass 7 made of a substance having a good heat conductivity, such as aluminum, and the radiating mass 7 is securely fixed to the body 3 in a surface contact relationship.
There are three adjusting members 4 and three screws 5 respectively on the circumference of a circle, centering around the optical axis, and the mechanism of mount adjustment is as illstrated in FIG. 1.
A portion 4b of each adjusting member 4 is a screw, and a confronting portion 4a is moved up and down by rotating the adjusting member 4.
Since the mount 1 is fastened downward by the screws 5, the mount 1 hits the confronting protion 4a of the adjusting members 4, and in this fashion the position is determined. Accordingly, by adjusting by means of rotating three adjusting members 4, it is possible to adjust the distance, and further the inclination, of the mount 1 with regard to the CCD surface.
In the conventional example described above, however, only the confronting portions 4a of the three adjusting members 4 receive the mount 1, and moreover the adjusting members 4 are only pressed down by the mount 1, not securely fixed. Hence, when there is applied vibration and the like to the body, the adjusting members 4 rotate, the confronting portions 4a move downward, the fastening by the screws 5 become looser, and finally there is a possibility of disconnection of the screws and further of the mount. It is possible to prevent the disconnection of the mount due to vibration and the like if the adjusting members 4 are screw-locked by adhesive, but readjustment becomes impossible once adjustment has been done and the adjusting members have been screw-locked.
It is known, however, that in the C mount lens to be mounted to an image input apparatus, there exist greater or smaller differences in the back-focus position (the position from the confronting portion 2a of the lens to the focusing surface) among lenses. Hence, it is necessary to perform a fine adjustment of the mount for each lens mounted on an image input apparatus. Accordingly, it is impossible to perform screw-locking of adjusting members, and thus the disadvantage of sensitivity to vibration has not been solved.